The present invention relates generally to the communication of multimedia information, such as multimedia information formatted pursuant to the RealTime Transport Protocol (RTP). More particularly, the present invention relates to apparatus, and an associated method, for converting realtime multimedia information, formatted in packet data form, such as that formatted pursuant to the RTP, into a form to facilitate transmission of the information on a radio channel. Operation of an embodiment of the present invention permits the communication of multimedia information by way of a cellular, or other radio communication system, with minimal and constant time delay while also communicating the information in a spectrally-efficient manner.
Advancements in communication technologies have permitted the introduction of, and popularization of, new types of, and improvements in existing, communication systems. Increasingly large amounts of data are permitted to be communicated at increasing thruput rates through the use of such new, or improved, communication systems. As a result of such improvements, new types of communications, requiring high data thruput rates, are possible. Digital communication techniques, for instance, are increasingly utilized in communication systems to efficiently communicate digital data, and the use of such techniques has facilitated the increased data thruput rates.
Multimedia communications, for instance, are exemplary of new types of communications permitted as a result of the improvements in communications technologies. Multimedia communications refer, generally, to the communication of more than one type of data between a sending station and a receiving station. Typically, the communication of such more than one type of data appears, to a user, to be simultaneous. Multimedia communications include, for instance, voice-over-data applications. Audio signals overlaid upon video signals used to effectuate teleconferencing is an example of a multimedia communication application. Two-way white board communication is exemplary of another multimedia communication application.
The different types of data exhibit different communication requirements. For instance, voice data must be communicated in real-time. That is to say, voice data must be communicated without significant delay and must be communicated in a manner which permits its reconstruction at a receiving station in a manner which introduces minimal time distortion. Otherwise, the voice data shall appear to be noticeably distorted. Conversely, non-voice data is not as time-sensitive. However, more stringent accuracy requirements are associated with non-voice data.
Multimedia communications can be effectuated utilizing packet data communication techniques. With the popularization of the Internet and communication thereon, standardized, multimedia protocols have been set forth by which to communicate multimedia information in a form amenable to its transmission by way of the Internet. An example of multimedia protocol is H.323. H.323 is a widely used ITU standard which uses RTP.
According to the H.323 protocol, when multimedia data is to be transmitted by a sending station, logical channels upon which to transmit the data are assigned. The data channels are allocated responsive to requests made by the sending station. Separate logical channels are requested for separate types of data. For instance, a first logical channel is requested upon which to transmit voice data, and allocation of a second logical channel is requested for transmission of non-voice data. A subset of the H.323 protocol, referred to as the H.245 protocol, defines the manner in which the channels are requested. Packets of data are thereafter transmitted upon the logical channels. In conventional manner, the individual packets include header information, such as IP, UDP and RTP information, to identify to where the packet is to be directed and to provide a time stamp with the packet. The information of a packet of data, referred to as the payload, is appended to the header information.
The H.323 protocol was intended originally for wireline communications, such as between communication stations, connected by wireline connections including those of the Internet. But, advancements in communication technologies have also permitted the widespread usage of radio communication systems. A cellular communication system is exemplary of a wireless communication system which has achieved wide levels of popularity and usage. Telephonic communication by way of a cellular communication system mimics communication by way of a conventional wireline, telephonic system. However, because a radio-link is utilized in a cellular, or other radio, communication system, bandwidth considerations are generally more significant than when wireline networks are utilized for communications. That is to say, the radio-link upon which communication is communicated in a radio communication system is of a limited bandwidth capacity. And, by reducing the bandwidth requirements of information communicated thereon, the information capacity of the radio-link can be increased. So, efforts are made to minimize the bandwidth requirements of signals transmitted over the radio-link.
Information communicated pursuant to an H.323 protocol is predicated upon a packet-data configuration. The header information required of each packet of data is relatively bandwidth-consumptive. As a result, communication of multimedia information by way of a radio-link, such as that formed in the operation of a cellular communication system, is a relatively inefficient manner by which to communicate multimedia information. However, because the RTP-based protocol has become a de facto standard by which to format multimedia information, multimedia stations shall likely continue to be operable pursuant to such protocol irrespective of the bandwidth inefficiency of communication of packet data by way of the radiolink.
If a manner could be provided by which more efficiently to communicate multimedia information by way of a radio-link, while still utilizing the RTP-based protocol at the sending and receiving stations, improved multimedia communications by way of a radio communication system could result.
It is in light of this background information related to multimedia communications that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, for converting real-time multimedia information formatted in packet-data form, into a form to facilitate transmission of the information on a radio channel. Through such conversion, the multimedia information can be transmitted with minimal time delay while also being transmitted upon the radio channel in a spectrally efficient manner.
In one aspect of the present invention, real-time media, which is part of multimedia information, is communicated between sending and receiving multimedia stations. On the communications path between the sending and receiving stations there is a communications link, such as a radio link, that has bandwidth limitations and spectrum efficiency requirements. In what follows, that link shall, at times, be referred to as the communications link. The multimedia information, when generated at a sending multimedia station, and when provided to a receiving multimedia station, is formatted in packet-data form according to an existing RTP protocol. Before transmission on the communications link, real-time media is converted into a communications-link format. Once converted into the communications-link format, the real-time media can be transmitted upon a special channel on the communications-link in an efficient manner. Once received, the real-time media is converted out of the communications-link format and back into the packet-data format before being sent to the receiving station. The same process takes place in the reverse direction. A special channel is defined as a channel that provides a constant bit rate. In a CDMA (code-division, multiple-access) communication system, the channel can be realized by a unique code by which the information to be communicated is encoded. In a TDMA (time-division, multiple-access) communication system, the channel can be realized by a time slot-frequency combination. Other ways to realize a special channel are possible.
A typical example of communications link is a radio link.
Consider the example of a cellular multimedia station communicating with a wireline multimedia station. At the cellular station, the outgoing multimedia information is converted into a radio-link format. Once converted into the radio-link format, the multimedia information can be transmitted upon the radio-link in an efficient manner. Once received, the multimedia information is converted out of the radio-link format and back into the packet-data format before being sent to the wireline station. The reverse process takes place in the reverse direction.
In one implementation, the multimedia stations include multimedia terminals. The multimedia terminals are operable to generate, and to receive, multimedia information formatted pursuant to a multimedia protocol such as H.323. Multimedia information is communicated between the multimedia terminals by way of a radio communication system, such as a cellular communication system.
Operation of an embodiment of the present invention converts the packet data-formatted information into a form to permit its efficient transmission upon a channel defined in the cellular communication system. The multimedia protocol provides for two components, a control plane and a user plane. The control plane includes an application signaling protocol, such as H.245 for H.323. The application signaling protocol specifies logical channels to be opened for the communication of the different types of multimedia information. Operation of an embodiment of the present invention monitors the application signaling and detects the opening and closing of logical channels defined in the control plane. Messaging to open a real-time media channel is translated into messaging to set up a special channel upon which to communicate multimedia information between the multimedia stations. Monitoring continues, and when the application signaling indicates that the logical channels are to be closed, the corresponding special channel is also closed.
As the multimedia protocol such as H.323 is increasingly being used in Internet Protocol (IP)-based communication systems to effectuate multimedia communications, operation of an embodiment of the present invention advantageously permits multimedia devices, operable pursuant to the protocol, to operate without alteration. Apparatus of an embodiment of the present invention monitors signals generated by such existing multimedia devices, and utilizes such signals to convert the multimedia information into a form more amenable for transmission upon a circuit-switched, or other, radio channel. Overhead data, such as IP, RTP and UDP headers associated with each packet of data, is removed prior to transmission of the multimedia information upon the special channel. Subsequent to transmission upon the special channel, multimedia information is reconverted back into packet-data format, and the header information is affixed again to the packets of data. Because the header information, otherwise forming a portion of each packet of data, is removed prior to transmission of the payload data, the same information is not repeatedly transmitted on the special channel. Improved spectrum efficiency results.
In these and other aspects, therefore, apparatus, and an associated method, is provided for converting packet-formatted multimedia information into a radio-link format. Once converted into the radio-link format, the multimedia information is amenable for transmission upon a radio-link extending between a first communication station and a second communication station of a radio communication system. A detector is coupled to receive indications of the packet-formatted data. The detector detects control plane information associated with the packet-formatted data. A requester is coupled to receive indications of detection by the detector of the control plane information. The requester requests allocation of a special channel defined by the radio-link extending between the first and second communication stations, respectively, for communication of the multimedia information thereon. A format converter is coupled to receive the packet-formatted data of which the multimedia information is formed. Responsive to allocation of the special channel requested by the requester, the format converter converts the packet-formatted data into the radio-link format. Thereafter, transmission of the multimedia information, formatted in the radio-link format, is permitted upon the special channel.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently preferred embodiments of the invention, and the appended claims.